This invention relates to a sectional motor winding circuit for use in starting three-phase motors. More particularly, the invention relates to such a winding circuit in which the motor has a pole pair number p=2 and an uneven slot number q (slots per pole and phase) which is larger than 1 and in which the motor winding, realized as a one-layer winding, is subdivided into two winding sections which are adapted to be switched on sequentially.
In one known sectional winding circuit for motor starting, the motor winding is subdivided into two equal winding sections and the winding coils associated with spatially immediately adjacent poles are tied together to form a winding section. Such a subdivision leads, especially in the case of an uneven slot number, to large operating asymmetries in the motor so that the rotor is stressed unilaterally by magnetic pull.
It is an object of the invention to provide a sectional winding circuit in which the rotor of the motor is not subjected to a unilateral magnetic pull when there is an uneven slot number q (q=slots per pole and phase) and in which thermal overloading during starting is prevented by reduction of the starting current.